1. Field of the Invention
This invention relates to a composition for intergranular insulation type semiconductor porcelain, which is improved in various electrical characteristics, particularly small in temperature coefficient, has high dielectric constant and is easy in handling, and a semiconductor porcelain and a capacitor by use of the composition.
2. Related Background Art
In recent years, with weight reduction and miniaturization of electronic circuit substrates and electronic instruments, a capacitor as one of the electronic parts is desired to be miniaturized with higher performance and the materials therefor have been actively developed. Among them, for its very high dielectric constant of 5.times.10.sup.4 to 7.times.10.sup.4, BaTiO.sub.3 type compositions for semiconductor porcelain and, for its little change ratio with temperature of electrostatic capacity and also small value of dielectric loss, SrTiO.sub.3 type compositions for semiconductor porcelain are attracting attention, respectively.
However, when a BaTiO.sub.3 type composition for semiconductor porcelain is used, there are involved the drawbacks such that the voltage dependence of electrostatic capacity is great, that the change ratio with temperature of electrostatic capacity is great, that waveform distortion is generated, that there is generation of noise due to electrostriction, that the dielectric loss under high voltage alternate current is great, that the change with lapse of time is great and that it is susceptible to thermal shock.
On the other hand, an SrTiO.sub.3 type composition for semiconductor porcelain has the drawbacks that it is smaller in dielectric constant as compared with the BaTiO.sub.3 type and also that management in steps in preparation of a capacitor can be done with extreme difficulty.
Further, in the case of SrTiO.sub.3 type, the change ratio with temperature of electrostatic capacity cannot satisfactorily be small as compared with BaTiO.sub.3 type. Particularly, in these days when the progress in electronic techniques is so rapid, it is necessary for obtaining a highly improved high performance device to improve various characteristics including those as mentioned above.
Particularly, it has been earnestly desired to develop a capacitor having high dielectric constant in the small value of temperature coefficient of dielectric constant. However, by use of the capacitor materials of the prior art, the relationship between dielectric constant and its temperature coefficient was such that the value of temperature coefficient becomes greater as the dielectric constant is made greater, and vice versa.
As another example, an intergranular insulation type semiconductor porcelain formed by use of the materials of the prior art had also the drawback that it is readily fractured.